Xerostomia (dry mouth) is a physiological phenomenon which is experienced in daily life. It gives sticky displeasure, makes speaking difficult, and causes bad breath. In its pathological state, it changes the oral microbial flora, thereby creating a failure in oral functions such as dental caries, periodontal disease, and mucosal infectious disease. Consequently, promoting salivary secretion and thereby wetting the oral cavity are important in making the oral cavity feel refreshed and preventing oral diseases.
So, it has been recognized that wetting the oral cavity is necessary to make the oral cavity feel refreshed and prevent oral diseases. To meet this requirement, there has been proposed the use of hyaluronic acid (which is a humectant) in WO00/56344. There has also been proposed an idea of positively promoting salivary secretion, thereby wetting the oral cavity. To materialize this idea, there has been proposed the use of a sialogogue selected from pickled Japanese apricot or Japanese apricot vinegar (in Japanese Patent Laid-Open No. Sho 56-22719) or organic acid (in Japanese Patent Laid-Open No. Hei 7-101856). There have also been proposed other sialogogues which do not resort to acid stimulation. Japanese Patent Laid-Open No. Hei 10-182392 discloses Cola nuts (Sterculiaceae) and Japanese Patent Laid-Open No. 2002-265375 discloses Capparis masaikai (Capparidaceae), Capparis pterocarpa Chun (Capparidaceae) and Centella asiatica (Umbelliferae).
Regrettably, hyaluronic acid produces the moisturizing effect but does not positively promote salivary secretion. Moreover, the above-mentioned sialogogues are limited in their use because they taste somewhat.